"40-60%RH is the ideal indoor air humidity. At this level, the airborne flu virus is quickly inactivated, and air humidity is below the level that promotes mold growth."
How Does Humidity Fight the Flu?
Research has shown that maintaining indoor humidity between 40-60% RH can help reduce airborne flu transmission by shortening the amount of time influenza viruses remain infectious. Proper humidity control is an important component of airborne infection control and healthier indoor environments. Learn more about humidity, health, and infection control below.
During the cold winter months, when heating systems dry the air, indoor humidity often drops into the dry danger zone of less than 40% RH. This results in more flu and respiratory infections spreading in the indoor air we all share. Using humidifiers to put moisture into an atmosphere is only way to ensure the ideal indoor humidity is maintained throughout the winter.
The nose and throat are our body's first line of defence in the fight against pollutants and microbes contained in the air we breathe. Their job is to filter, humidify and heat the air before it enters more sensitive parts of our respiratory system and causes damage.
A central part of this defence mechanism is a layer of tiny hair-shaped structures, called cilia, inside our respiratory tract and a thin membrane of mucous that covers them. Airborne pollutants, such as particles, allergens, viruses and bacteria, are captured by this sticky mucous membrane and removed from the air. The mucous layer traps and clears most potential intruders into our airways and serves as a defensive "moving carpet lift".
The tiny cilia whip back and forth many times per second to transport the mucous and its freight towards our throats. It is then swallowed or coughed out and therefore destroyed or rendered harmless.
If the air we are breathing is below 40% RH (relative humidity) over a prolonged period of time, this mucous membrane layer dries out. This can cause damage to the cilia; inhibits our ability to filter pollutants from the air we breathe and leave us susceptible to airborne infection.
Mucous membranes in our respiratory tract trap airborne pollutants and tiny cilia transport them to our pharynx, where they are swallowed or coughed out.
In low humidity environments below 40%RH our mucous membranes dry and this "mucociliary clearance" process is impaired. This leaves us more susceptible to airborne infections, like the flu or common cold.
Effects of humidity on the human body
Humidification Approved for Healthcare
Exploring the relationship between humidity and temperature
Why 40-60% relative humidity is recommended
or expert guidance?
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